With cron, you can use some shortcuts that let you see when an entry is triggered without remembering the more difficult numbers that you would have to put there:
Synonym Meaning and equivalent crontab values
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@reboot Run once, at startup (only works with this synonym)
@yearly Run once a year, equals "0 0 1 1 *".
@annually (same as @yearly)
@monthly Run once a month, equals "0 0 1 * *".
@weekly Run once a week, equals "0 0 * * 0".
@daily Run once a day, equals "0 0 * * *".
@midnight (same as @daily)
@hourly Run once an hour, equals "0 * * * *".
Keep in mind that you can fine tune the time a script is run by cron with numeric values. These shortcuts are just easier to remember.